Iceland waits for volcanic shoe to drop

Icelandic communications links and even transatlantic flights could be disrupted by a second, more destructive volcano following this weekend's eruption.

Some 500 people were evacuated from their homes after the Eyjafjallajökull volcano 120 kilometres south-east of Reykjavik shot ash and molten lava into the air on Saturday night.

Initial fears that the eruption had occurred directly beneath the Eyjafjallajökull glacier – which could have caused glacial melt, flooding and mudslides – proved unfounded.

But volcanologists have warned that previous Eyjafjallajökull eruptions have triggered eruptions of neighbouring Katla, one of the largest volcanoes in Iceland. Katla erupted every 40 to 80 years in the thousand years before the last eruption in 1918.

"The eruption is long overdue at Katla and there is quite a bit of anxiety in Iceland about the potential size of eruption," says Dave McGarvie of the Open University in Milton Keynes, UK.

Coast changer

The larger volcano, beneath the larger Mýrdalsjökull glacier, has a reputation for triggering huge jökulhlaup – the Icelandic term for the sudden release of meltwater from glaciers and ice sheets. Its last eruption generated a peak discharge of 1.6 million cubic metres per second within 4 to 5 hours and moved so much debris that Iceland's coastline was extended by 4 kilometres.

A new Katla eruption would be unlikely to kill anyone, because the area is sparsely populated and eruptions are usually preceded by earthquakes that would give plenty of time to evacuate. It would cut the main road link in the south of the island, however.

Because the lower atmosphere is thinner closer to the poles, the giant cloud of fine particles released would more easily reach the stratosphere – where aircraft cruise – than would dust from volcanoes in most other countries. Depending on the wind, this could disrupt air travel in the north Atlantic, forcing aircraft travelling between the UK and Scandinavian countries and North America to take slower, more expensive routes further south than normal.

History repeats

The three eruptions of Eyjafjallajökull in the last 1100 years – in 920, 1612 and 1821 – have all triggered larger Katla eruptions.

"With the current methods we have of resolving the plumbing systems of these volcanoes we can't explain why one triggers the other, but we know there is a symbiotic relationship," says McGarvie.

Iceland is well prepared for volcanoes, with sophisticated monitoring systems combining GPS, seismometers and satellite data as well as established civil defence plans.

A quarter of the island's population died from the famine that resulted from the 1783 eruption of the Laki volcano, the worst in modern times in high latitudes. It sent a huge cloud of haze across Europe and parts of North America, triggering dramatic climatic changes, from the largest recorded snowfall in New Jersey to one of the longest droughts seen in Egypt.

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